Efficacy and Safety Study of Ontamalimab as Maintenance Treatment in Participants With Moderate to Severe Crohn's Disease (CARMEN CD 307)

Inclusion Criteria:

• Participants and/or their parent or legally authorized representative (LAR) must havean understanding, ability, and willingness to fully comply with study procedures andrestrictions.
• Participants must be able to voluntarily provide written, signed, and dated (personally or via a LAR) informed consent and/or assent, as applicable, toparticipate in the study.
• Participants must have completed the 16-week induction treatment period from studySHP647-305 (NCT03559517) or SHP647-306 (NCT03566823) and met the following criteria atbaseline in maintenance study SHP647-307:

1. Meet endoscopic response criteria of a reduction in SES-CD from induction studiesSHP647-305 (NCT03559517) or SHP647-306 (NCT03566823) baseline by greater than orequal to >=25% at Week 16 of induction studies SHP647-305 (NCT03559517) orSHP647-306 (NCT03566823) or
2. Meet at least 1 of the following 4 criteria at baseline in maintenance studySHP647-307, in addition to no worsening of endoscopic score as measured by SES-CDrelative to induction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823) baseline:

• Achieving clinical remission as determined by meeting the criteria for clinicalremission using the 2-item PRO, that is, 2-item PRO sub scores of average worst dailyabdominal pain <=3 (based on 11-point NRS) over the 7 most recent days* and averagedaily stool type frequency <=2 of type 6/7 (very soft stools/liquid stools) as shownin the Bristol Stool Form Scale (BSFS) over the 7 most recent days*.
• A decrease of at least 100 points in CDAI score (CDAI-100) from induction studiesbaseline.
• A decrease of >=30% and at least 2 points from induction studies baseline in theaverage daily worst abdominal pain over the 7 most recent days*, with the averagedaily stool frequency of type 6/7 (very soft stools/liquid stools) either: (i) notworsening from induction studies baseline and/or (ii) meeting the criteria forclinical remission, that is, 2-item PRO subscore of average daily stool frequency <=2of type 6/7 (very soft stools/liquid stools) as shown in the BSFS over the 7 mostrecent days*.
• A decrease of >=30% from induction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823) baseline in the average daily stool frequency of type 6/7 (very softstools/liquid stools) as shown in the BSFS over the 7 most recent days*, with theaverage daily worst abdominal pain either: (i) not worsening from induction studiesSHP647-305 (NCT03559517) or SHP647-306 (NCT03566823) baseline and/or (ii) meeting thecriteria for clinical remission, that is, 2-item PRO sub score of average worst dailyabdominal pain <=3 (based on 11-point NRS) over the 7 most recent days*. *Note: The 7 days may or may not be contiguous during the 10 days of data collectionbefore colonoscopy preparation, depending on days to be excluded because of missingdata. If fewer than 7 days are available, the criterion will be calculated on allavailable most recent 6 or 5 days. If fewer than 5 days are available, the criterionwill be treated as missing.
• Participants receiving any treatments for CD are eligible provided they have been, andare anticipated to be, on a stable dose for the designated period of time.

Exclusion Criteria:

• Participants who had major protocol deviations (as determined by the sponsor) ininduction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823).
• Participants who permanently discontinued investigational product because of an AE,regardless of relatedness to investigational product, in induction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823).
• Participants who are likely to require surgery for CD during the study period, exceptminor interventions (eg, seton placement for anal fistulas).
• Participants are females who became pregnant during induction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823), females who are lactating, females who areplanning to become pregnant during the study period, or males or females ofchildbearing potential not agreeing to continue acceptable contraception methods (ie,highly effective methods for female participants and medically appropriate methods formale participants) through the conclusion of study participation.
• Participants who do not agree to postpone donation of any organ or tissue, includingmale participants who are planning to bank or donate sperm and female participants whoare planning to harvest or donate eggs, for the duration of the study and through 16weeks after last dose of investigational product.
• Participants who, in the opinion of the investigator or the sponsor, will beuncooperative or unable to comply with study procedures.
• Participants who have developed obstructive colonic stricture, or enterovesical orenterovaginal fistulae during the induction study SHP647-305 (NCT03559517) orSHP647-306 (NCT03566823).
• Participants who have a newly diagnosed malignancy or recurrence of malignancy (otherthan resected cutaneous basal cell carcinoma, squamous cell carcinoma, or carcinoma insitu of the uterine cervix that has been treated with no evidence of recurrence).
• Participants who have developed any major illness/condition or evidence of an unstableclinical condition (example [eg,] renal, hepatic, hematologic, gastrointestinal (except disease under study), endocrine, cardiovascular, pulmonary, immunologic [eg,Felty's syndrome], or local active infection/infectious illness) that, in theinvestigator's judgment, will substantially increase the risk to the participant if heor she participates in the study.
• Participants with any other severe acute or chronic medical or psychiatric conditionor laboratory or ECG abnormality that may increase the risk associated with studyparticipation or investigational product administration or may interfere with theinterpretation of study results and, in the judgment of the investigator, would makethe participant inappropriate for entry into this study.
• Participants with known exposure to Mycobacterium tuberculosis (TB) since testing atscreening in induction studies SHP647-305 (NCT03559517) or SHP647-306 (NCT03566823)and who have been advised to require treatment for latent or active disease but whoare without a generally accepted course of treatment.
• Participants with any of the following abnormalities in hematology and/or serumchemistry profiles during the evaluation of the last visit in the induction studiesSHP647-305 (NCT03559517) or SHP647-306 (NCT03566823). If the results are considered bythe investigator to be transient and inconsistent with the participant's clinicalcondition, may be repeated once prior to enrollment in Study SHP647-307.

1. Alanine aminotransferase (ALT) and aspartate aminotransferase levels >= 3.0 × theupper limit of normal (ULN).
2. Total bilirubin level >=1.5 × ULN or >2.0 × ULN if the participant has a knowndocumented history of Gilbert's syndrome.
3. Hemoglobin level <=80 gram per liter (g/L) (8.0 gram per deciliter [g/dL]).
4. Platelet count <=100 × 10^9/L (100,000 cells per cubic millimeter [mm^3]) or >=1000 × 10^9/L (1,000,000 cells/mm^3).
5. White blood cell count <=3.5 × 10^9/L (3500 cells/mm^3).
6. Absolute neutrophil count<2 × 10^9/L (<2000 cells/mm^3)
7. Serum creatinine level >1.5 × ULN or estimated glomerular filtration rate <30milliliter per minute (mL/min)/1.73 m^2 based on the abbreviated Modification ofDiet in Renal Disease Study Equation.

• Note: If platelet count is <150,000 cells/mm^3, a further evaluation shouldbe performed to rule out cirrhosis, unless another etiology has already beenidentified.
• Participants who are investigational site staff members or relatives of those sitestaff members or participants who are sponsor employees directly involved in theconduct of the study.
• Participants who are participating in other investigational studies (other thaninduction studies SHP647-305 [NCT03559517] or SHP647-306 [NCT03566823]) or plan toparticipate in other investigational studies during this study.